In conventional installation switch devices, the connecting conductor is screwed to a connection plate, which includes a screw hole and is mounted so as to be stationary in the interior of the device, by means of a terminal screw including a screw head and a screw shank. The connecting terminal arrangement is located in a terminal socket including an opening for inserting the connecting conductor and an opening providing access to the screw head for actuating the terminal screw with a tool, for example a screwdriver. When the connecting conductor is clamped, the screw shank penetrates the annular terminal shoe and is in threaded engagement with the screw hole.
Conventional installation switch devices are, for example, circuit breakers, motor circuit breakers or fault-current circuit breakers, the connecting terminal arrangement of which is formed specifically to connect a connecting conductor to an annular terminal shoe, in particular a terminal shoe with a closed ring. A hole through which the terminal screw is guided upon clamping is thus provided in the annular terminal shoe. Terminal screws which include a flat head and a long shank and which are screwed into a connection plate in the interior of the switch device housing are used in the known conventional installation switch devices. In this way, the terminal shoe is clamped between the screw head and the connection plate, optionally with an additional thrust piece inserted therebetween. Attached to the connection plate are further conductors which lead into the interior of the device and carry the current path through the installation switch device between an input terminal and an output terminal.
A connecting conductor having an annular terminal shoe cannot be clamped between the screw head and the connection plate unless the terminal screw has been completely unscrewed and lifted off the connection plate beforehand in such a way that a passage is formed at the insertion opening for the closed terminal shoe. During this process, the terminal screw may fall out and be lost through the access opening. Inserting the terminal screw after the connecting conductor including the annular clamping shoe has been introduced requires skill from the engineer, since, due to the long shank and the flat head of the conventionally-used terminal screws, it is easy for said screws to tilt in the terminal socket between the access opening and the thread in the connection plate in such a way that the screw shank does not come into threaded engagement with the screw thread of the connection plate.
An object of the present invention is therefore to develop a conventional installation switch device in such a way that the terminal screw cannot be lost when connecting a connecting conductor with an annular terminal shoe and it is easier to screw in the terminal screw.